The present invention relates to a magneto-optical disk drive system with a mechanism for retracting a magnetic head out of sliding contact with a magneto-optical disk, when the main power supply of the magneto-optical disk drive system is turned off. The present invention also relates to a mechanism for allowing a disk cartridge to be manually ejected from a system housing also when the main power supply of the magneto-optical disk drive system is turned off.
Magneto-optical disk drive systems are capable of rewriting desired information many times on erasable magneto-optical disks. In such a magneto-optical disk drive system, a laser beam of large power, emitted from an optical head, is continuously applied to the recording layer of a loaded magneto-optical disk to heat small spots or bits on the magneto-optical disk to the Curie point. Then a biasing magnetic field is applied to the spots by a biasing magnetic field generator or magnetic head to magnetically align the spots in an initial direction. Thereafter, the biasing magnetic field is reversed and a laser beam of large power is intermittently applied to the spots, which are magnetically realigned, thus, recording information.
Rewriting one track of information on a magneto-optical disk is relatively slow because it is necessary to rotate the magneto-optical disk in both erasing and recording cycles. To eliminate this drawback, there has recently been proposed a magnetic-field- modulated overwrite magneto-optical disk drive system which selectively applies an N or S magnetic field to small spots on a magneto-optical disk where a laser beam is to be converged. The proposed magnetic-field- modulated overwrite magneto-optical disk drive system can rewrite one track of information on the magneto-optical disk simply by rotating the magneto-optical disk only once.
Quick overwriting on the magneto-optical disk requires that a magnetic field, which is modulated at high speed, be applied to the magneto-optical disk, and a small-size magnetic head be positioned very closely to the recording layer of the magneto-optical disk. To meet such requirements, the magnetic head is fixed to the free end of a cantilevered flexible arm mounted on a rear surface of a magnetic head carriage, such that the magnetic head bends slightly toward the magneto-optical disk when the magnetic head is in its free state. When the magnetic head is in its loading position, it is displaced upwardly under an air pressure developed by rotation of the magneto-optical disk and held at a highly close distance to the surface of the magneto-optical disk.
In the event that the magneto-optical disk drive system is abruptly turned off due to a power supply failure, for example, while information is being written on the magneto-optical disk by the magnetic head that is in the loading position, the magneto-optical disk gradually slows down as it is not positively rotated by its drive motor but rotated only by inertia. The magnetic head that has been displaced upwardly under the air pressure exerted by the rotating magneto-optical disk, now falls into sliding contact with the magneto-optical disk that is rotating by inertia, and may possibly be damaged by the contact with the magneto-optical disk.